1. Field of the Invention
The present invention relates to an image forming apparatus, such as an electronic copying machine, and, more particularly, to an image forming apparatus having a document feeding unit for automatically picking up a manually inserted document so as to set it on a document table, and discharging it upon formation of an image.
2. Description of the Related Art
In a conventional image forming apparatus of this type, a document feeding unit comprises a wide endless conveyor belt arranged at a cover portion overlapping a document table, and a belt driving mechanism for driving the conveyor belt. With this arrangement, a document which is manually inserted into a predetermined position is fed and set onto the document table or a document on the document table is discharged therefrom by driving the conveyor belt.
In the conventional image forming apparatus, when the document feeding unit is used, a document is set on the document table with reference to a right scale opposite to a left scale on the exposure start side which is used as a reference when a document is manually set.
With the conventional apparatus, document set positions with respect to the document table vary depending on whether a document is manually set or set by the document feeding unit. For this reason, when the document feeding unit is to be used, the exposure start position needs to be switched to the right reference, resulting in complicated control and structure of an exposure mechanism.